Trying to find mass given force, distance, and time.

[jad6016]

Homework Statement

A dockworker applies a constant horizontal force of 70.0 N to a block of ice on a smooth horizontal floor. The frictional force is negligible. The block starts from rest and moves a distance 11.0 m in a time 4.80 s

Homework Equations

A)What is the mass of the block of ice?
B)If the worker stops pushing at the end of 4.80 s, how far does the block move in the next 4.20 s?

The Attempt at a Solution

A)F=m*a, 70.0=x*11.0/4.80
70.0/(11.0/4.80)=x, x=30.5 which was wrong.
B)I have absolutely no idea where to start or what to do on this part.

 

[tiny-tim]

welcome to pf!

hi jad6016! welcome to pf!

A)F=m*a, 70.0=x*11.0/4.80

no, you've used a = distance/time, which is wrong …

use one of the standard constant acceleration equations to find a

 

[yromelyn]

find first the acceleration
derive the d=vit+1^2at^2
that's what i think